Antennas having the capability of multiple frequency band operation are known in the art. It is desirable to provide isolation between the multiple frequency bands. Conventionally this is done by filtering the bands by filters outside the antenna body, which requires added hardware and space.
It is known to use a spiral antenna for one band, with other spiral antennas placed at the edges of larger spirals. The outer spiral is generally quite small and therefore must operate at a significantly different and higher frequency. If the spirals are close to the same frequency, they take up much more space and are therefore not a compact structure.
Generally, antennas that are spaced close to each other have considerable coupling which reduces the antennas's ability to separate out signals.